A. Field of the Invention
The present invention relates generally to the field of basic process function controllers, thermostatically controlled apparatus and oven control arrangements and more particularly to latch control apparatus for self-cleaning ovens.
B. Description of the Prior Art
Various arrangements of the prior art provide control arrangements for the locking of the oven door of a self-cleaning oven during the self-clean cycle and when the oven temperature is above a predetermined temperature.
These prior art arrangements include various door latching arrangements and control circuits for controlling the locking and unlocking of the oven door.
U.S. Pat. No. 4,109,637 discloses a locking mechanism for the door of a self-cleaning oven including a latch arm movable between a door locking position and a door unlocked position with a pair of solenoids coupled to the rear of the latch arm by a respective movable magnet bar. The magnet bars are simultaneously displaced for each separate energization of the solenoids. One of the solenoids in energized to move the latch arm to the locked position at the start of the clean cycle. The second solenoid is energized after the clean cycle when the oven temperature has dropped below 550.degree. F. to move the latch arm to the unlocked position. Separate thermostat contacts from the oven thermostat are utilized to control the second solenoid that moves the latch arm to the unlock position. A switch is provided for each solenoid and is disposed and operated by the movable magnet bar of each respective solenoid. The contact state of each switch is determined by and each switch is directly actuated by the position of each respective solenoid magnet bar. The switches control the connection of the electrical supply to the respective solenoid coils for energization of the respective solenoids. Thus, the position of each solenoid magnet bar is utilized along with the timer circuit and the unlock thermostat to energize and de-energize each solenoid.
U.S. Pat. No. 3,469,568 discloses a latch control arrangement and self-clean control circuit including a latch position switch 100 disposed to be actuated by the engagement of a lock member 90 that moves to lock a latch striker 71. The switch 100 is incorporated into the self-clean control circuit to enable the self-clean mode. A latching rod 94 is provided to latch the lock member 90 in the latched position and to prevent the unlocking of the oven door by restricting the movement of the lock member 90. The latching rod 94 is withdrawn from interfering relationship with the lock member 90 by an unlock arrangement including thermostatic contacts 44 on the thermostat AT and an unlock solenoid 110. Thus, the switch 100 does not measure the position of the latching rod 94 that prohibits the unlocking of the oven door during the self-cleaning cycle.
U.S. Pat. No. 3,823,294 in FIG. 5 discloses a door locking system including a solenoid actuated lock means 22 that protrudes into a lock groove 25 in the door 21. A switch 3 including an actuating lever 26 is contacted by the rear end of the solenoid core opposite the lock means 22 to sense the locked position of the lock means 22. In FIG. 6, another door lock structure is disclosed including an electromagnetically driven, rotatable latch 28. The latch 28 includes a hook 30 for latching engagement within a recess position 32 of the oven door 21. A switch 3 senses movement of the rear end of the latch 28 opposite the hook portion 30. A second switch 9 functioning as an emergency stop switch includes a switch actuator 37 operable by an operating button 39 and a push bar 38.
U.S. Pat. No. 4,013,312 discloses a door latch assembly including a locking plate 40 having an edge portion 91 that engages and operates a switch 90. The switch 90 is connected in a power supply circuit. A locking rod 66 is positionable to prevent movement of the locking plate when a locking finger 65 of the locking rod 66 engages an abutment 71 of the locking plate 40.
U.S. Pat. No. 4,101,750 discloses a door interlock system for use with a microwave oven and including a slider member 58 movable between released and interlocking positions. A primary door interlock switch 27 and a secondary door interlock switch 24 are actuated when the door is in the closed, latched position and incorporated in the microwave control circuitry. A monitor switch 28 is provided and is actuated by a latch arm 82. A latch arm 81 actuates the secondary interlock switch 24. The primary interlock switch 27 is operated by a movable arm 72 that rotates in response to movement of the handle 15. The latch arms 81 and 82 are fixed to a bar attached to the door 14. The slider 58 is moved to the latching position by operation of the handle 15 wherein slider pins 60, 61 engage the latch arms 82, 81 respectively to latch the door.
While the prior art arrangements referred to hereinbefore are generally suitable for their intended use, the prior art arrangements do not provide for the direct verification of the locking member of an oven control circuit being in locked engagement with a latch member by means of a locking member verification switch actuated by the locking portion of the locking member that engages the latch member and prevents movement thereof. Without the direct verification of the position of the locking member, inaccurate sensed conditions of the locked condition of the oven door can result in undesirable operating modes without the secure locking of the oven door. Further, the prior art arrangements do not provide an automatic safety latch control arrangement utilizing efficient and reliable energization arrangements to control the automatic locking and unlocking of the oven door and control circuitry that directly senses the operation of the latch arrangement, the mode position of the latch arrangement and the position of the oven door to ensure proper operation.